1. Field of the Invention
The present invention relates to a method and an integrated system for torque control and energy storage enabling the realization at the same time of the storage of energy, the regulation of the on board supply voltage and the control of the torques applied in a space vehicle.
2. Description of the Prior Art
In conventional systems of the prior art, there have been used chemical energy storage and attitude control, these two functions being independant. Attitude control includes three principal elements, namely sensors, an electronic attitude control circuit and torque generators. The complexity of these elements is essentially a function of the type of mission to be carried out by the space vehicle. The sensors are constituted by a combination of solar sensors, ground sensors, star sensors and an inertial or gyroscope reference system. The electronic circuit can be either of the wired type or of the programmed type with the use of a microprocessor. In these conventional systems, the torque generators are generally effected by means of kinetic moment exchanges, that is to say by means of momentum wheels or reaction wheels, or by means of gas ejection. In such systems, the regulation of the line voltage produced by a solar generator is totally independent of the attitude control. Any modification of the load being manifested by a variation in the busbar voltage, it is then necessary to provide a shunt regulator which maintains the load resistance constant. This regulator operates practically permanently and absorbs the surplus power which is dissipated in the form of heat. This dissipation must take place towards the exterior of the vehicle on account of the problems of thermal control, which necessitates relatively complex devices. To be able to provide momentarily for energy requirements higher than the possibilities of the solar generator, there is used a battery controlled by a charge generator and a discharge regulator.
Subsequently, it appeared possible and desirable to replace the chemical storage of energy (fuel cells, Ag--Zn or NiCd or NiH.sub.2 batteries) by kinetic energy storage using inertia wheels constituted by dynamo-electric machines with an inertial flywheel operable both as a motor and as a generator. Such a storage device is, for example, described in Applicant's French patent application No. 76.10158 filed 7 Apr. 1976. Kinetic storage is more advantageous than chemical storage notably on account of its performance with respect to the mass energy utilisable and the life span. However, kinetic storage produces an effect reacting directly on the attitude vehicle since the electrical energy-kinetic energy transfer is accompanied by a torque which, on account of the reaction principle, is applied to the structure of the vehicle. It is hence possible, if one uses kinetic energy storage, to couple the energy storage and the attitude control.
On this basis, NASA has already proposed a system, called IPACS ("Integrated Power/Attitude Control System"), effecting at the same time the storage of energy and the piloting of a space vehicle. In this system, the storage system can deliver important torques necessary for piloting or minimize the torques during operations of energy transfer. This is achieved either by wheels mounted on a single or double gimbal joint, or by the use of several assemblies of counter-rotating wheels and the final piloting of the vehicle is produced by reaction wheels. In this system, all the functions are interdependent which requires a review of the optimal configuration for each mission. Thus the arrangement and the design of the wheels differ for each case contemplated.
It is an object of the present invention to utilize to the maximum the advantages of kinetic energy storage without having the restrictions of the IPACS which encompasses both the functions of energy storage and of attitude control of the whole of the space vehicle.
It is a further object of the present invention to provide an integrated system for torque control and energy storage which produces the energy storage and delivers the torques required by the attitude control, but in which the attitude control in itself is independent of the system.